This invention relates generally to igniting solid propellants and more specifically to igniting the propellants in a way that reduces the alteration of the composition of the propellant combustion products by the combustion products from the ignition device.
One method of investigating the smokiness of a solid propellant formulation is to load a small rocket motor with the propellant being investigated, static fire the motor in an environmentally controlled chamber, and observe the combustion products that are exhausted from the motor. If the observation is to produce an accurate evaluation, the propellant must be ignited in a way so that the ignition device will not add smoke to the propellant combustion products. Mixtures of powdered metals and pulverized oxidizers which have been commonly used to ignite propellants being tested for smokiness have combustion products containing particulate salts which appear as smoke. These salts can interfere with evaluations made on a propellant even though the weight ration of ignition material to the propellant in a motor is only 1 or 2%. There is therefore a need to ignite charges of propellant being evaluated for smokiness by a means other than the common ignition materials. This need led to the present invention which ignites solid propellants without adding smoke contaminants to the combustion products of the propellants.
The invented igniter differs from a conventional pyrogen type igniter in that a pyrogen has a propellant charge of specific physical dimensions. The propellant in this invented igniter has no specific physical dimensions but rather is finely divided sperical particles or sheet fragments in order to achieve much larger burning surfaces and shorter burning times than are found in pyrogen type igniters.